"We're quite worried about wrecks off the coast in southwest Sweden," which are viewed as maritime treasures, University of Gothenburg marine biology researcher Christin Appelqvist told the English-language online newspaper The Local.
Shipworms are not worms at all, but rather saltwater clams with reduced shells notorious for boring into and eventually destroying wooden structures immersed in sea water, such as piers, docks and wooden ships.
Until now, shipworms had not infiltrated the Baltic because of its cold temperatures and low salt content. But the Teredo navalis species -- one of 65 varieties found in the world, best known for concentrations in the Caribbean Sea -- has recently made its way into the Baltic, especially along the Danish and German coasts, the researchers say.
The influx may be stem from warmer seas caused by climate change, Appelqvist says.
"The warmer temperatures mean that the shipworm is less stressed and can thus tolerate lower salinity," she tells the newspaper.
To protect the 100,000 well-preserved shipwrecks scattered across the bottom of the Baltic, the Gothenburg team has joined WreckProtect, an European Union project designed to determine exactly which archaeological treasures are at risk.
"We just don't know today how far Teredo navalis may spread," but the marine creatures are unlikely to make it as far north as Stockholm, on Sweden's south-central east coast, Appelqvist said.
The group is also exploring ways of protecting the shipwrecks from shipworm destruction by covering them with permeable geotextile fabrics and bottom sediment.
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